This proposed research is designed to focus on the antigens and their participatory role in the rejection of allografts. The Principal investigator has developed a large clinical transplant service and has had a long interest in the basic machinery of allograft rejection. Several years ago it was shown that the skin stimulated the lymphocytes in a one-way fashion and that this was immunospecific and represented a skin specific antigen. The technique allowed fine discrimination of the Ag-B locus in the rat. Recently the use of 2-mecapthoethanol to allow the stimulation of the lymphocytes by the kidney cells when dissociated under proper conditions raises the possibility that kidney specific antigens can be detected using the same technique as well as other organ specific antigens. Hence, the Principal Investigator has recruited Dr. Sakai, a research surgeon who has developed many innovative techniques in microvascular surgery. Hence, this project is to utilize the rat model with microvascular surgical techniques to correlate both the in vivo and in vitro responses. Hopefully, the in vivo responses of various organ rejections as measured by the in vitro organ cell-lymphocyte culture reaction as a measure of organ specific antigens will allow more minute prediction of graft survival under immunosuppression. Ultimately, it is expected that this information can be used clinically to better select donor-recipient pairs for transplantation.